Well evacuator

ABSTRACT

The nature of the invention is the use of WELL-EVACUATOR™ to extract and convey polluted liquid and vapor from wells to the surface for separation and treatment. This technology is an alternative to use of conventional well pumps alone or in combination with soil vapor extraction or two phase extraction. Three applications are presented; circulated water supplied as prime mover to eductor(s), compressed air prime mover, and soil vapor extraction blower in combination with WELL-EVACUATOR™. All three rely on use of a prime mover such as water or air supplied to a jet to create a vacuum capable of extracting and conveying water and soil vapor under pressure from a well to separation and treatment equipment at the surface. If the well head is sealed, a vacuum is created in the subsurface enhancing removal of contaminants. These novel applications allow use of commercially available equipment.

BACKGROUND OF THE INVENTION

[0001] A method and apparatus for removal of soil gas and groundwater inthe subsurface and separation and treatment facilities are disclosed.This invention, WELL-EVACUATOR™, relates generally to a process andapparatus for extraction of liquid and vapor from below surface using anejector or jet powered by air, steam or water or other prime movers, toentrain and convey vapor and liquid to the surface for separation andtreatment. System designs will vary depending on application. As anexample, tests were conducted at a gas station in Sebastopol, Calif. Inthe first test contaminated groundwater was extracted under vacuum froma single and multiple wells using a surface mounted centrifugal pump andeductor. In a second test, an eductor was positioned near the bottom ofa well and compressed air was used to extract and convey well water andsoil vapor to a separator activated carbon treatment system at thesurface.

[0002] Removal of liquids and gases from the subsurface has been acontinuing problem throughout human history. In the last century aconsiderable amount of pollutants including gasoline, oil, chlorinatedsolvents, and volatile organic compounds have found their way into thesubsurface at numerous sites. Often these sites are difficult andexpensive to remove by conventional means such as excavation ofcontaminated soil or extraction of groundwater using underground wellpumps, followed by treatment (pump and treat). Contaminated sites usingpump and treat, such as those found in Santa Clara, Calif. can requireover one hundred years to restore at a cost of hundreds of millions ofdollars. More reliable and/or robust technologies such asWELL-EVACUATOR™ offer promise for reducing costs and time forrestoration of these environmentally distressed properties.

[0003] Centrifugal and reciprocating subsurface, well pumps have beensuccessfully used to convey water from the subsurface for centuries. Inpermeable formations they remain the equipment of choice for manyapplications. In low permeability formations, low water flows, sedimentinclusion and corrosion, often make these pumps expensive to maintainand operate. These problems are compounded by the need to remove soilvapor and groundwater under negative pressure (vacuum) at contaminatedsites. Low flows of liquid in combination with low pressure can causecavitation, overheating, and eventual failure of pumps. Small volume,air operated, reciprocating pumps help reduce these problems however,maintenance and operating costs are still high. Recent advancements suchas 2-Phase® Extraction (2PE), and air sparging eliminate the need forsubsurface pumps. In 2PE a tube is inserted into the formation and waterand soil gas are aspirated to the surface under high vacuum, where it isseparated and treated. This technology has been demonstrated to beeffective for removal of contaminants in low permeability soilsformations such as clays and fine silts. However, due to the complexityand costs for equipment, licensing, operation and maintenance, 2PE isoften not selected. Also, energy costs for aspiration of water undervacuum is high, as compared to transport of soil gas and groundwaterutilizing WELL-EVACUATOR™ technology. Air injection has also been usedsuccessfully at sites. Air is sparged into a well and the air bubblescarry water and soils vapor to the surface where they are separated andtreated. High volumes of compressed air are needed and the treatmentsystem costs are proportional to these high volumes. This technologydoes not provide the higher vacuums possible using SVE orWELL-EVACUATOR™. Therefore application of this technology is limited.

[0004] To minimize the deficiencies of conventional technologies theinvention, utilizes unique technologies to remove and conveycontaminated liquid or vapor or combination thereof to separation andtreatment equipment at the surface.

[0005] In the first application, an ejector is mounted near the bottomof a well with provision of a conduit for introducing compressed air (orother prime mover) from equipment at the surface. The well is sealed atthe top to prevent leakage of outside air into the well. Introduction ofcompressed air into the ejector creates a vacuum at the inlet initiallyentraining water that is conveyed to the surface under pressure. Insites having low permeability, such as soils with clay or fine silt,water depth eventually decreases to below the extraction jet inletallowing both soil vapor and groundwater in combination to be aspiratedto the surface. Displacement of the water and vapor creates a vacuum inthe well and the surrounding area (area of influence). Air at thesurface is drawn into the formation causing volatile contaminants suchas gasoline to evaporate and be swept into the well and conveyed to thesurface for treatment. Removal of volatile contaminants in the vaporphase is commonly referred to as soil vapor extraction (SVE). Thistechnology is highly effective in removing gasoline from the subsurfaceespecially in combination with groundwater removal.

[0006] In a second application, a surface mounted jet pump is utilizedto extract contaminated liquid, vapor or combination thereof and conveyto separation and treatment equipment. The jet pump is connected tosingle of multiple wells. A single jet eductor is connected directly tothe pump for shallow wells (liquid depth less than 25 feet). Deep wellsrequire a separate eductor for each well be connected to the bottom ofeach extraction tube with provisions for supplying circulated water. Airseparators are installed at the surface to prevent vapor locking the jetpump when the liquid level drops below the extraction tip(s) of any ofthe wells, allowing the entrance of soil gas.

[0007] In a third application, a surface mounted jet pump or compressedair is utilized to remove and convey liquid and small quantities ofvapor from the subsurface as described above. A blower or vacuum pump isconnected to the top of the well to remove relatively large volumes ofvapor.

[0008] Each site is unique. Pilot testing is often conducted todetermine which application will result in the least cost and healthrisk required to remove contaminants.

[0009] This invention has several advantages. Ejectors have no movingparts. Maintenance is therefore minimal. Air, water and steam are ofteneither existing, on-site or equipment is commercially available. Asimple liquid/gas separator followed by activated carbon for is oftenthe only equipment needed for treatment of soil vapor and groundwaterprior to discharge. No exotic vacuum pumps, coolers, and related oilseparation equipment are needed. No subsurface moving parts to maintain.Controls and maintenance are minimized. Operation is simplified,minimizing labor and training. The combined capital, operating andmaintenance savings are often significant in comparison with otheravailable technologies. This invention provides a much needed technologyfor economic, energy efficient, simplified subsurface dewatering andcleanup of volatile organic compound (VOC) contaminated groundwater andsoils.

BRIEF SUMMARY OF THE INVENTION

[0010] This invention relates to a vacuum ejector designed to entrainliquid, vapor or liquid and vapor combined from the subsurface andtransmit through a conduit to above ground where it can be separated,treated, and discharged as appropriate. The simplicity of an ejectorovercomes problems with conventional pumps and vapor extraction systemscommonly employed in remediation of contaminated sites or pumps used fordewatering excavations.

[0011] An ejector is connected to a source of compressed air (or otherprime mover source). The unit is mounted in a conduit allowing enoughroom for air and gas to flow to the surface in the annular space createdbetween pipes. At the well head, the lines are separated; the compressedair is connected to a compressor, and the liquid vapor line is routed toan air/water separator followed by activated carbon beds. The well headis sealed using a slip connector that allows insertion and positioningof the ejector in the bottom of the well and prevents short-circuitingof atmospheric air.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] To clarify the concept of the invention a brief description ofthe attached drawings follows.

[0013]FIG. 1 is an elevation section view of an assembled ejector unitconstructed in accordance with this invention and inserted into ascreened well designed for removal of both contaminated soil gas andgroundwater.

[0014]FIG. 2 is an elevation section view of an assembled ejector unitconstructed in accordance with this invention and inserted into ascreened well designed for removal of groundwater. Soil vapor is removedthrough a separate conduit at the top of the well and connected to SVEequipment or a separate eductor.

[0015]FIG. 3 is a conceptual drawing of the optional liquid/gasseparator and carbon adsorption treatment system.

[0016]FIG. 1A is a prior art section view drawing a 2PE extraction pipein the bottom portion of a well.

[0017]FIG. 1B is a prior art section view drawing of air sparge pipe inthe bottom portion of a well.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Reference FIG. 1:

[0019] An ejector 26 is mounted inside a conduit 6 with provision forcompressed gas or liquid 20. The unit 10 is inserted in screened well 4with the ejector at or below the water table 18. Slip joint seals 22prevent outside air from entering well and provide means for adjustingejector elevation in combination with flexible conduits (such as hose ortubing) 20 and 28. As compressed air flows through the ejector 26throat, a vacuum is created at the inlet 8 entraining soil gas 14 andgroundwater 16 that is discharged from ejector outlet 30 into conduit 6.Gas and liquid travel up conduit 6 to the surface and enter conduit 2wherein they are routed to gas/liquid separator 40. A mesh pad 50 withinthe gas/liquid separator 40 entrains and coalesces liquid in the gasstream before exiting the unit. Liquid 54 exits the bottom. Pump 56circulates portion of water, where applicable, to well eductor. Vapor 52exits from the top. Activated carbon units 42 adsorb volatile organiccompounds (VOC) from liquid and gas streams. Treated ground water 44 andsoil gas 46 are discharged to sewer and atmosphere respectively.Dehumidified air 50, produced by expanding compressed air, is blendedwith soil vapor to enhance adsorption capacity of carbon whereapplicable.

[0020] Reference FIG. 2:

[0021] An ejector 92 is mounted inside a conduit 95 with provision forcompressed gas or liquid 80. The unit 90 is inserted in screened well 86with the ejector at or below the water table 18. Slip joint seals 88prevent outside air from entering well and provide means for adjustingejector elevation in combination with flexible conduits (such as hose ortubing) 94 and 96. As compressed air flows through the ejector throat92, a vacuum is created at the inlet 98 entraining soil gas 14 andgroundwater 16 that is discharged from ejector outlet 93 into conduit96. Gas and liquid travel up conduit 95 to the surface and enter conduit84 wherein they are routed to gas/liquid separator 40 and subsequentcarbon adsorption system described above.

[0022] Reference FIG. 1A:

[0023] In prior art design for air sparging, compressed air 64 entersconduit 60 and is discharged 62 near bottom of well 66. Gas bubbles riseto the surface in the well and entrain soil gas 14 and groundwater 16.At the surface the soil gas and groundwater travel out the well 70, arecollected, separated and treated as appropriate to meet environmentalrequirements.

[0024] Reference FIG. 1B:

[0025] In prior art design for 2PE, soil gas 14 and groundwater 16 enterwell 4 and are aspirated under high vacuum into conduit 30. Conduit 30is connected to a vacuum system at the surface. Liquid and gas aretreated as appropriate to meet environmental requirements.

[0026] Groundwater and soils vapor extraction using a down-hole ejector,is a simple solution to an age-old problem. Centrifugal andreciprocating pumps are costly to install, operate and maintainespecially in ‘tight’ low permeability formations. An ejector has nomoving parts and can run long periods without maintenance or operatingover-site. Commercially available, off the shelf, air compressors andejectors in a variety of sizes are readily available for purchase orlease. Above ground equipment can operate at or above atmosphericpressure eliminating the need for additional pumps. Simple activatedcarbon systems can often be used to remove many volatile organiccontaminants prior to disposal.

[0027] Other possible variations include surface mounted ejector forgroundwater extraction. A perfect vacuum is the equivalent ofapproximately 30′ water column. Therefore for shallow aquifers, ejectorscan be mounted directly to a centrifugal or similar pump. Multiple wellscan be manifolded to the suction line to the pump to simplifyinstallation, operation and maintenance of an extraction system.

[0028] Another variation is to have two separate ejectors—one forgroundwater and a second sized for soil vapor. The groundwater ejectoris considerably smaller and mounted near the bottom of the well. Thesoil vapor ejector is installed at ground level thereby simplifying andreducing piping, costs and energy required.

[0029] Another variation is to connect a blower for removing vapor fromthe top of the well and using a groundwater ejector mounted near thebottom of the well.

[0030] Another variation is to orient the eductor vacuum inlet along thesame axis as the discharge.

[0031] Still another variation is to provide separate piping for primemover and discharge lines connected to eductor.

[0032] One skilled in the art may appreciate that additional embodimentsmay be contemplated, including alternative piping and treatmentarrangements.

[0033] In the foregoing description, certain terms have been used forbrevity, clarity, and understanding, but no unnecessary limitations areto be implied there from beyond the requirements of the prior art,because such words are used for description purposes herein and areintended to be broadly construed. Moreover, the embodiments of theapparatus illustrated and described herein are by way of example, andthe scope of the invention is not limited to the exact details ofconstruction.

What I claim is: 1) A process for extracting, conveying, separating andtreatment of contaminated liquid and vapor from the subsurface whichcomprises: a) providing extraction tube(s) in well(s) with jeteductor(s) positioned below or above ground to remove liquid, vapor or acombination thereof, over a portion or the entire length of the well(s);b) piping, or fittings, and manifolds for supplying prime moverincluding but not limited to water, air, or steam to eductor(s) withinwell(s) and collection of liquid and vapor discharged from wells; c)footcheck valve(s) at the end of extraction tube(s) to prevent reversedflow; d) strainers to prevent check valves from plugging; e) piping toconvey vapor and liquid from eductor to above ground equipment; f)vessel for liquid/vapor separation; g) vapor treatment equipmentincluding but not limited to activated carbon, aluminum oxide, molecularsieves, biofilters, catalytic oxidation, combustion; h) pump(s) forconveying liquid to equipment for storage and treatment; i) tank forstorage of liquid; j) liquid treatment equipment including but notlimited to activated carbon, aluminum oxide, air stripping, combustion,activated sludge, molecular sieves; k) instrumentation for control andmonitoring of process parameters; l) pumps, boilers, air compressors forsupplying prime mover(s); m) seal(s) at well head(s), boring(s) oropening(s) with provisions for facilitating piping or tubing, so that avacuum applied within the extraction tube will extract gases and liquidsfrom the subsurface but not above the seal. 2) A process for extracting,conveying, separating and treatment of contaminated liquid and vaporfrom the subsurface which comprises: a) providing extraction tube(s) inwell(s) with eductor(s) positioned below ground to remove liquid over aportion or the entire length of the well(s). Vapor blower(s), fan(s),eductors or other vacuum devices attached to well head to convey vaporto surface mounted separation and treatment units. b) piping, orfittings, and manifolds for supplying prime mover including but notlimited to water, air, or steam to eductor(s) within well(s); c)footcheck valve(s) at the end of extraction tube(s) to prevent reversedflow; d) strainers to prevent check valves from plugging; d) piping toconvey vapor and liquid from eductor to above ground equipment; e)vessel for liquid/vapor separation; f) vapor treatment equipmentincluding but not limited to activated carbon, aluminum oxide, molecularsieves, biofilters, catalytic oxidation, combustion; g) pump(s) forconveying liquid to equipment for storage and treatment; h) tank forstorage of liquid; i) liquid treatment equipment including but notlimited to activated carbon, aluminum oxide, air stripping, combustion,activated sludge, molecular sieves; j) instumentation for control andmonitoring of process parameters; k) pumps, boilers, air compressors forsupplying prime mover(s); l) seal(s) at well head(s), boring(s) oropening(s) with provisions for facilitating piping or tubing, so that avacuum applied within the extraction tube will extract gases and liquidsfrom the subsurface but not above the seal. 3) A process for extracting,conveying, separating and treatment of contaminated liquid from multiplewells or openings from the subsurface which comprises: a) providingextraction tubes in wells with jet eductors positioned above ground andmanifolded to remove liquid, over a portion or the entire length ofmultiple wells b) piping, or fittings, and manifolds for supplyingliquid to eductors within wells and collection of liquid and vapordischarged from wells; c)foot check valve(s) at the end of extractiontube(s) to prevent reversed flow; d) strainers to prevent check valvesfrom plugging; e) piping to convey vapor and liquid from eductor toabove ground equipment; f) vessel for liquid/vapor separation to preventcavitation, loss of prime and/or air locking pump; g) liquid treatmentequipment including but not limited to activated carbon, aluminum oxide,air stripping, combustion, activated sludge, molecular sieves;